Conventional laser beam machines are disclosed, for example, in Japanese Patent Publication No. SHO 62-11953. FIG. 8 shows configuration of the conventional type of laser beam machine including an optical scanning system, while FIG. 9 shows part of the laser beam machine partially modified. In FIGS. 8 and 9, the reference numeral 1 indicates a laser oscillator for outputting a laser beam 2, which laser beam 2 is deflected by a bend mirror 3 to be lead to a machining lens 4. The laser beam 2 is converged by the machining lens 4 and applied to a workpiece 5, whereby laser machining is performed.
FIG. 8, i.e., the figure showing the conventional type of device, illustrates a one-axis laser beam machine including an optical scanning system. This machine has a configuration in which a machining head section 6 holding the bend mirror 3 and machining lens 4 is driven and moved for scanning in the X direction using well-known ball screws, a linear guide, and a servo motor or the like each not shown herein to execute machining such as cutting.
In the conventional type of device, an expandable light path sealing protector, i.e., a light path bellows 7, is provided for protecting a portion of a transfer path transferring the laser beam 2; a opposite light path bellows 8 is symmetrically connected to the side opposite to the light path via a communicating box 9.
Designated by the reference numeral 10 in FIG. 8 is an inspection hole cover of an inspection hole for adjusting the bend mirror 3 and inspecting for maintenance thereof in the communicating box 9. It will be appreciated that guide rollers 11, each of which is attached at an appropriate position to the light path bellows 7 and the opposite light path bellows 8, ride along a guide rail 12, i.e., a mechanism for guiding the guide rollers 11. FIG. 9 shows an alternative configuration in which an opening edge of the opposite light path bellows 8 is attached to the side face of the machining head section 6.
Next description is made of the operations associated with the conventional laser beam machines illustrated in FIGS. 8 and 9. In particular, it will be noted that the transfer path of the laser beam 2 from the laser oscillator 1 to the machining lens 4 comprises the light path bellows 7, communicating box 9 or bend mirror 3, opposite light path bellows 8 and machining head section 6, which elements cooperatively form a sealed room. The inside of this sealed room is filled with a clean gas (normally, clean air or dry air) which gas does not interfere with transfer of the laser beam 2 and does not contaminate the bend mirror 3 and machining lens 4. Thus, the sealed room protects the laser beam transfer path from the entrance of contaminated gas from outside of the transfer path. It will be appreciated that the presence of contaminated gas, e.g., a volatile gas, is well known to be a laser interfering gas for a carbon dioxide laser. It should be mentioned that the term "contaminated gas" indicates either a gas mixed with the volatile gas or dust, either of which will interfere with laser operation.
When the machining head section 6 is driven, for instance, in the + X direction, the light path bellows 7, the moving direction of which is restricted by the guide rollers 11 and the guide rail 12, expands while the opposite light path bellows 8 shrinks, and vice versa. The machining head section 6 is operated during movement thereof so that the pressure of the clean gas in the sealed room will always be kept at a substantially constant level to move the clean gas between the bellows 7 and 8 via either the communicating box 9 or the cylinder of the machining head section 6. For this reason, contaminated gas and dust cannot enter the laser beam transfer path from the outside.
The conventional type of laser beam machine including an optical scanning systems illustrated in FIGS. 8 or 9 requires a communicating box 9, which makes the device complicated and high priced. It will also be appreciated that the access to the bend mirror 3 for maintenance is not optimal. Moreover, as shown in FIG. 9, i.e., in the configuration in which the opposite light path bellows 8 is asymmetrically attached to the machining head section 6, the guide rail 12 for the light path bellows 7 cannot be shared with that of the opposite light path bellows 8. Thus, a guide rail is required specifically for support of the opposite light path bellows 8, which makes the device more complicated and more expensive. Furthermore, an opposite light path bellows 8 is required in addition to a light path bellows 7, which makes the device basically complicated and expensive. The problems with conventional laser beam machines of this type is increased in a multi-axis moving type machines. In particular, the opposite light path bellows 8 is rather an obstacle, which causes other performance characteristics of the machine, for instance, operability or the like, to suffer.
Furthermore, although a device using a pressure adjusting buffer tank is disclosed in Japanese Patent Publication No. SHO 62-11953, there have recently been pointed out several problems with the device. For example, the configuration of the laser beam machine becomes more complicated, particularly with respect to the enlargement of the area required for installation. This is due to the fact that the external dimensions of the pressure adjusting buffer tank included in the device are required to be much larger, i.e., in proportion to the drivable range of the device. Moreover, for the case wherein the laser beam transfer path is constructed with a member such as a bellows having a comparatively low degree of sealing performance, the path has been known to gradually permit contaminated gas to migrate from the outside of the laser beam transfer path to the inside, mostly in portions of the sealed room relatively far away from the pressure adjusting buffer tank. For this reason, it is necessary to maintain a high degree of sealing by using components in the light path, a combination including a duct fitted with an O ring, which makes the configuration even more complicated and expensive.